Bio-dynamic monitoring, diagnosis and follow-up of Abdominal Aortic Aneurysms using optical imaging techniques

腹主动脉瘤（AAA）是一种局部的腹主动脉球囊样扩张。它造成每10万人中至少45人死亡，对老年人构成严重威胁。目前，血管内主动脉修复（endovascular aortic repair， EVAR）是AAA最常见的治疗方法，它是一种微创治疗方法，在主动脉内放置可扩展的支架（endoprosthesis）。内假体的主要问题是渗漏和移位。由于内漏，动脉瘤囊会在全身血压的作用下返回，这可能导致破裂。动脉瘤囊内的压力几乎无法测量。这种测量与其他指标（超声或CT扫描）一起，将极大地帮助确定是否需要再干预。过去的研究表明，测量由于心脏跳动而在腹部形成的机械波可以间接指示囊压，并且有可能用作EVAR前后的诊断和监测信号。在之前对其中一位申请者的预研究中，使用了激光振动计来测量腹部表面的振动。这一过程相当繁琐，也没有对病人进行彻底的检查。在这个项目中，我们想研究几种光学技术来间接监测AAA囊压力的变化。特别是，数字图像相关（DIC）技术似乎很有希望用于这一应用。DIC是一种相当简单的技术，基于立体视频图像来测量表面的三维运动（目前用于工程应用）。这种光学技术尚未用于医学成像。尽管诸如DIC之类的光学技术有可能为诸如AAA监测和诊断等医疗应用开辟一个全新的领域，但它们尚未被尝试用于监测医疗状况。该项目是机械工程学院和TUM医学院的合作项目。

Abdominal aortic aneurisms (AAA) is a localized balloon-like dilation of the abdominal aorta. It accounts for the death of at least 45 individuals per 100,000 population and is a serious threat to aging people. Nowadays, endovascular aortic repair (EVAR) is the most common treatment for AAA. It is a minimally invasive treatment in which an expandable stent graft (endoprosthesis) is placed within the aorta. Major problems of endoprostheses are leakage (endoleak) and migration. Due to endoleaks, the aneurysm sac comes back under systemic blood pressure, which can cause rupture. The pressure inside the aneurism sac is nearly impossible to measure. Such a measurement, together with other indicators (ultrasound or CT scan), would greatly help determining the need for a reintervention. In the past, it has been shown that measurement of the mechanical wave forming on the abdomen due to the heart beat can be an indirect indication of the sac pressure and has the potential to be used as a diagnostics and monitoring signal before and after EVAR. In the previous pre-study of one of the applicants, a laser-vibrometer was used to measure the vibration of the abdomen surface. The procedure was rather cumbersome and also no thorough tests on patients were undertaken. In this project, we want to investigate several optical techniques to indirectly monitor the change of the AAA sac pressure. In particular, Digital Image Correlation (DIC) techniques seem promising for this application. DIC is a rather simple technique based on stereo video images to measure 3D motion of a surface (nowadays used in engineering applications). Such optical techniques are not yet used in medical imaging. Optical techniques such as DIC have not yet been tried to monitor medical conditions although they have the potential to open a whole new field for medical applications such as AAA monitoring and diagnosis. The project is a cooperation between the faculty of Mechanical Engineering and the School of medicine of TUM.